[TZAR]

This is all beutifaul work in theory BUT you need to look a a spring which is bolted into a car first.

You will notice that the centre section is flat due to the fact the spring plates and diff saddle compressing the spring flat. This then make you springs work in two sections rather than one long sweeping arc..
It also removes some of the length of the spring due to it being RIGID.(for calculations.)

Just an extra part of the equasion to consider.

[JrZook]

TZAR wrote:

This is all beutifaul work in theory BUT you need to look a a spring which is bolted into a car first.

You will notice that the centre section is flat due to the fact the spring plates and diff saddle compressing the spring flat. This then make you springs work in two sections rather than one long sweeping arc..
It also removes some of the length of the spring due to it being RIGID.(for calculations.)

Just an extra part of the equasion to consider.

This is a good aspect in terms of the simple equation as it accounts for theoretical maximum possible spring length which is when it's dead flat.

Obviously it will never reach this point as you elaborated on above. This is a good thing in terms of using the equation to find out whether or not the shackle will unload and collapse against the chassis. The bend in the spring adds lee-way rather than subtracting it.

Again this is a mathematical/theoretical approach that will get you pretty dam close to a solution that works rather than starting with no measurements at all.

Dan

[Teracis]

I am posting here so I can find this thread again.
Hopefully I don't lose the notepad I just wrote on that tells me I need 990mm centre to centre for the spring hangers with 65mm EFS rear springs all round. At least I know I can read back through this thread and get the information if when required.

EDIT: Edited as per JRZOOK's post below this.

[JrZook]

JrZook wrote:

EFS rears are one of the longest mains that can fit under a zuk rear with stock shackles. The stock rear bracket eye-eye center-line spacing of a sierra is 985mm. This is absolute minimal borderline spacing required for the length of these leaves with stock shackles and descent bushes. Why did I say that? Because once the EFS pack have lost a few leafs and therefore are actually able to work and flex to the stock bumpstops, I have seen now 2 cases where the EFS rears have unloaded and collapsed the shackle on to the chassis rail. Of course I never heard/saw this until i designed my springs to be the exact same length as EFS rears mine shackles also collapsed as well....


So what im trying to conclude here is that 985mm spacings for a RUF is dead borderline with new bushes/shackles and most likely will unload the shackle. Go for 990mm if using the standard shackle. This is what I have with EFS length mains and haven't had an issue yet.

I would probably re-think your 986mm spacings

[Teracis]

JrZook wrote:

JrZook wrote:

EFS rears are one of the longest mains that can fit under a zuk rear with stock shackles. The stock rear bracket eye-eye center-line spacing of a sierra is 985mm. This is absolute minimal borderline spacing required for the length of these leaves with stock shackles and descent bushes. Why did I say that? Because once the EFS pack have lost a few leafs and therefore are actually able to work and flex to the stock bumpstops, I have seen now 2 cases where the EFS rears have unloaded and collapsed the shackle on to the chassis rail. Of course I never heard/saw this until i designed my springs to be the exact same length as EFS rears mine shackles also collapsed as well....


So what im trying to conclude here is that 985mm spacings for a RUF is dead borderline with new bushes/shackles and most likely will unload the shackle. Go for 990mm if using the standard shackle. This is what I have with EFS length mains and haven't had an issue yet.

I would probably re-think your 986mm spacings

I'm four beers in and just listening to what Ballbag is telling me (sitting beside me yapping about springs e.t.c. after I showed him my post in the noob talk shocks thread) I didn't even know this thread was here despite him telling me he's told me about it more than once, I've edited my above post to reflect what you have said, I pretty much posted in here so I can read the whole thread while I'm sober another day and understand what is going on.

Everything sounds good though, definitely going to have bulk travel if the maths is correct!

[Teracis]

Just read the entire thread and am quite happy with all the maths going on here. Thanks for having already calculated the 990mm spacing for EFS rears, I will be measuring this afternoon and making plans to make this the new measurement between spring hangers all round. Hopefully the RUF that is already on the chassis is on the money although I'd imagine given that it's 80mm extension from standard I doubt it will be. The rear should be easy since it's only 15mm over the standard 975mm quoted in this thread.

I have to remember that we are talking about dead straight from eye to eye, not measuring along the chassis or anything silly like that! Should make it even easier to setup as it's a direct line with the tape and less room for error!

JrZook did you happen to have the calculations handy you used for shock travel with this model?

[sideways]

I made an excel spreadsheet to calculate all this out, thought I would share. Change the numbers in the blue and it calculates it out for you.

Screen cap.

Attachment:

Clipboard02.jpg

Enjoy.

[pete_79]

sideways wrote:

I made an excel spreadsheet to calculate all this out, thought I would share. Change the numbers in the blue and it calculates it out for you.

Screen cap.

Attachment:

Clipboard02.jpg

Enjoy.

Thanks for sharing this mate.
It has been good to use this for double checking what I've found with my 'suck it and see' approach is actually mathematically correct as well...

I used a bit of timber to support the full length of the spring when compressing it, so it was totally flat and measured more like 1008mm for the standard rear spring length.
Not sure how much variation there would be in manufacturing but, that 8mm difference in spring length was the the fine line between success and failure, both mathematically and practically.